Contact switch device



1963 R. A. BOENNING ETAL 3,111,608

CONTACT SWITCH DEVICE 2 Sheets-Sheet 1 Filed Feb. 27, 1961 70 EXTERNALRELAYS,

COUNTERS E 7'6.

ROBERT A. BOENNING LEON S. OTIS INVENTORS FIG.3. BY

2 Sheets-Sheet 2 BOENNING OTIS INVENTORS ATTORNEY (ROBERT A. LEON s.

i Q kemm u R. A. BOENNING ETAL CONTACT SWITCH DEVICE Nov. 19, 1963 FiledFeb. 27, 1961 Patented Nov. 19, 1963 3,111,608 CONTACT SWITCH DEVICERobert A. Boenning, 1800 Ramblewood Road, Baltimore 14, Md, and Leon S.Otis, 3697 Ramona Circle,

Palo Alto, Calif., assignors of one-third to Walter G.

Finch, Catonsville, Md.

Filed Feb. 27, 1961, Ser. No. 91,889 10 Claims. (Cl. 317-146) Thisinvention relates generally to electric circuit makers, and moreparticularly it pertains to a touch responsive switch apparatus.

In psychological and biological research, it is frequently desirable touse a touch or contact response switch device to operate counters,kymographs and other recording equipment. In industry, it is ofadvantage to cause electrical devices to turn on or off by similar lighttouch or even proximity effect.

An example of the use of an electronic contact switch is in the studiesof fluid consumatory behavior of animals or in research on tastesensitivities or preferences for various solutions. A switch of thistype permits the recording of every lap of the tongue of the animal aswell as the frequency and distribution of the laps.

Because the driving signal is an alternating current, the net ionizationis zero, with the taste perception being unaltered. Corresponding usageof such an electronic contact switch device in industry would be forpackage counting, burglar alarms, door bell or elevator signal buttonsand the like.

A true touch responsive switch requires no effort to manipulate, and, inaddition, no sensation of its functioning is perceptible to theoperating organism.

Accordingly, it is an object of this present invention to provide acontact switch arrangement for imperceptibly closing an electriccircuit.

Another object of this invention is to provide a nonreactive touchcounting system.

And another object of this invention is to provide a touch or proximityoperated circuit closing device which makes definite, rapid circuitryclosure for each touch or approach thereof, however indefinite.

And still another object of this invention is to provide a touch switchdevice which will not overload and which can be set to ignore indefinitetrains of triggering associated with a positive touch.

And still another object of this invention is to provide a switch devicewhich will be frequency-selective.

These and other objects and attendant advantages of this invention willbecome more readily apparent and understood from the following detailedspecification and accompanying drawings in which:

FIG. 1 is a schematic diagram of an electrical contact switch deviceincorporating features of the present invention;

' FIG. 2 is a schematic perspective of a laboratory setup employing thenovel contact switch device of FIG. 1;

FIG. 3 is a schematic perspective of a modification of the laboratorysetup shown in FIG. 2;

FIG. 4 is a time phase diagram of the operation of the electricalcontrol switch device of FIG. 1;

FIG. 5 is a schematic diagram of an emitter follower front end stage forincreasing the input impedance of the amplifier of the contact switchdevice of FIG. 1, for proximity operation; and

FIG. 6 is a schematic diagram of a series resonant circuit added to thefirst stage for frequency selective operation.

Referring now to the details of the drawings, the contact switch deviceillustrated in the electrical circuit of FIG. =1 is designated generallyby reference numeral 10. This contact switch device 10 consistsbasically of a cascade amplifier arrangement formed of two commonemitter connected transistors T and T and a monostable multivibratorconsisting of two transistors T and T A relay K provides for theexternal circuitry closure.

As will be further described and illustrated in FIGS. 1 and 4, the touchsignal or trigger consists of an impulse of sinusoidal wave form, forexample, a signal of 8,000 cycles per second which is applied by theanimal to contact P of any desired type.

A short connection is made therefrom to a capacitor C and thence to thebase of the transistor T The amplified output of transistor T the touchsignal A of FIG. 4 is, in turn, applied to the base of the transistor Twhich is biased such that clipping occurs at a low input amplitude.

The output of transistor T is then a square wave, shown as the clippedamplified signal B in FIG. 4, which is passed through a differentiatingnetwork consisting of a capacitor C and a resistor R to produce sharppositive and negative spikes. The negative spikes are removed by asemi-conductor diode D leaving a differentiated and rectified outputsignal C which consists of a series of positive trigger pulses, one foreach positive square wave loop, with the number of signal pulses beingdetermined by the duration of the touch contact response itself.

The trigger signal pulses are then applied to the multivibratortransistors T and T through a coupling capacitor C The time constant ofthe multivibrator which, as previously pointed out, consists oftransistors T and T is adjusted such that conduction is transferred fromtransistor T to transistor T for a period of approximately 450microseconds, in the example, so that each fifth trigger pulse of thedifferentiated and rectified output signal C will retrigger the circuit.

As a result, the relay K in the collector circuit of the transistor T isenergized for approximately of the switching cycle with no currentflowing through it for the remaining 10% (as shown by signal W in thewave form D of FIG. 4). Because of the mechanical inertia of thearmature of the relay K and the electrical inertia of its coil, therelay K cannot follow the very short oif period and it remains closed asshown in its operation cycle E as long as trigger pulses of thedifferentiated and rectified signal C are supplied. Consequently, therelay K closes on the first trigger pulse and it opens and remains openafter the last of a consistent group, with each relay operationcorresponding to one complete onoff contact. Depending on the type ofrelay used, contacts by the tongue of the animal R, on the contact P, inexcess of 25 per second can be reliably followed by the relay K Thedriving signal for the system is supplied by an oscillator 12, shown inFIGS. 2 and 3, having a low impedance output. This driving signal may beapplied directly to a ground-isolated metal floor 14 upon which theanimal R stands and makes electrical contact therewith as shown in FIG.2, or to spaced metal plates 16 and 18, as shown in FIG. 3, betweenwhich the animal R stands. If the resistance of a rat is estimated at100,000 ohms, a signal applied directly to the floor 14 need have only amagnitude of approximately 0.2 volt to reliably trigger themultivibrator in the prototype apparatus. A higher voltage is needed,which can be found by trial and error, where the signal is applied byspaced plates 16 and 18 as mentioned above in connection with FIG. 3.

The use of a multivibrator time constant of approximately 450microseconds, in the prototype apparatus, insures freedom from responseto stray transients X (as shown in the curve of the touch signal A) thatmay find their Way into the circuit, as shown in FIG. 4, since atransient is not periodic and therefore cannot trigger the multivibratorfor the number of cycles sufficient to activate the relay K even thoughit produces a clipped signal and a differentiated pulse Y and Z inwaveforms B and C, respectively. Also, because of the low powerrequirements of the transistorized contact switch device 10, theoperation is extremely economical for long time operation and completelyeliminates problems due to heat generation.

A relay K is typically used to switch another (external) relay havingmultiple contacts with high current ratings in order to operatecounters, stepping switches and other circuit elements as desired.

The addition of an emitter follower stage as shown in FIG. 5, ahead ofthe first stage as illustrated in FIG. 1 permits proximity operation.When the animal R of FIG. 2, for example, nears the sensory plate shownin FIG. 5, the operating signal is capacitively coupled to the base ofthe transistor T of FIG. 5, which, in turn, couples the signal, at lowimpedance, to the base of transistor T of FIG. 1, through the capacitorC to effect operation as previously described.

The addition of a frequency selective circuit, consisting of inductor Land capacitor C of FIG. 6, ahead of the first stage of FIG. 1, permitsfrequency selective operation. Two or more contact switch devices,consisting of the circuits of FIG. 2 and FIG. 6 as stated may beconnected to a common point, P of FIG. 6, the common point connected, inturn, to oscillators, the frequencies of which match the resonantfrequencies of the tuned circuits. If an oscillator is then switched on,the contact switch device with the series resonant circuits resonant atthe oscillator frequency will be triggered and operation will be aspreviously described.

This frequency selective device can be utilized, for example, toactivate electrical circuits, by means of relay K in response toprogramming signals coded with respect to frequency.

Obviously many modifications and variations of the present invention arepossible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

l. A contact switch apparatus responsive to the presence of an object tooperate a pair of spaced contacts, comprising, means to supply analternating current signal, amplifying means to convert said alternatingcurrent signal to a square wave output signal, said amplifying meansbeing electrically connected to said means to supply an alternatingcurrent signal by the presence of said object and said square waveoutput signal being representative of the duration of the presence ofsaid object as Well as being indicative of its presence per se, meansfor converting said square wave output signal to unidirectional pulses,means for providing a substantially constant duration current pulse fromsaid unidirectional pulses, and means for utilizing said substantiallyconstant duration current pulse to actuate said pair of spaced contacts.7

2. A contact switch apparatus responsive to the presence of an object tooperate a pair of spaced contacts, comprising, means including anoscillator to supply an alternating current signal, amplifying means toconvert said alternating current signal to a square wave output signal,said amplifying means being electrically connected to said oscillator bythe presence of said object and said square Wave output signal beingrepresentative of the duration of the presence of said object as well asbeing indicative of its presence per se, means to convert said squarewave output signal to unidirectional trigger pulses, means for providinga substantially constant duration current pulse from said triggerpulses, and means for utilizing said substantially constant durationcurrent pulse to actuate said pair of spaced contacts.

3. A contact switch apparatus responsive to the presence of an object tooperate a pair of spaced contacts, comprising, means including anoscillator to supply an alternating current signal, amplifying means toconvert said alternating current signal to a square wave output signal,said amplifying means being electrically connected to said oscillator bythe presence of said object and said square wave output signal beingrepresentative of the duration of the presence of said object as well asbeing indicative of its presence per se, means to convert said squarewave output signal to unidirectional trigger pulses, means responsive toa predetermined number of said trigger pulses to provide a constantduration current pulse therefrom, said last mentioned means beingre-triggered by trigger pulses which exceed said predetermined numberthereof to provide subsequent constant duration current pulses, meansincluding a relay responsive to said constant duration current pulses toactuate said pair of spaced contacts.

4. -A contact switch apparatus responsive to the presence of an objectto operate a pair of spaced contacts, comprising, means including anoscillator to supply an alternating current signal, amplifying means toconvert said alternating current signal to a square wave output signal,said amplifying means being electrically connected to said oscillator bythe presence of said object and said square wave output signal beingrepresentative of the duration of the presence of said object as well asbeing indicative of its presence per se, means to convert said squarewave output signal to unidirectional trigger pulses, means responsive toa predetermined number of said trigw ger pulses to provide a constantduration current pulse therefrom, said last mentioned means beingre-triggered by trigger pulses which exceed said predetermined numberthereof to provide subsequent constant duration current pulses separatedfrom each other by a momentary current stoppage, means including a relayresponsive to said constant duration current pulses to actuate said pairof spaced contacts, said relay having sufficient inertia to remainsubstantially unalfected by said momentary current stoppage.

5. The contact switch apparatus of claim 4 wherein said means responsiveto a predetermined number of said trigger pulses has a time constant tothereby be unaffected by trigger pulses resulting from transient outputsignals from said oscillator.

6. The contact switch apparatus of claim 4 wherein said object iselectrically conductive.

7. The contact switch apparatus of claim 4 wherein the alternatingcurrent signal supplied by said oscillator is of low impedance.

8. A contact switch apparatus as recited in claim 4, wherein saidunidirectional pulses are regularly spaced.

9. A contact switch apparatus as recited in claim 4, and additionally adevice for changing the input impedance of said unidirectional pulseproviding means.

10. A contact switch apparatus as recited in claim 4, and additionallycircuit means for rendering said unidirectional pulse providing meansfrequency selective.

Parrish: Rectifiers and Circuits for DC Relays, Electronic Design, Nov.15, 1956, page 22.

1. A CONTACT SWITCH APPARATUS RESPONSIVE TO THE PRESENCE OF AN OBJECT TOOPERATE A PAIR OF SPACED CONTACTS, COMPRISING, MEANS TO SUPPLY ANALTERNATING CURRENT SIGNAL, AMPLIFYING MEANS TO CONVERT SAID ALTERNATINGCURRENT SIGNAL TO A SQUARE WAVE OUTPUT SIGNAL, SAID AMPLIFYING MEANSBEING ELECTRICALLY CONNECTED TO SAID MEANS TO SUPPLY AN ALTERNATINGCURRENT SIGNAL BY THE PRESENCE OF SAID OBJECT AND SAID SQUARE WAVEOUTPUT SIGNAL BEING REPRESENTATIVE OF THE DURATION OF THE PRESENCE OFSAID OBJECT AS WELL AS BEING INDICATIVE OF ITS PRESENCE PER SE, MEANSFOR CONVERTING SAID SQUARE WAVE OUTPUT SIGNAL TO UNIDIRECTIONAL PULSES,MEANS FOR PROVIDING A SUBSTANTIALLY CONSTANT DURATION CURRENT PULSE FROMSAID UNIDIRECTIONAL PULSES, AND MEANS FOR UTILIZING SAID SUBSTANTIALLYCONSTANT DURATION CURRENT PULSE TO ACTUATE SAID PAIR OF SPACED CONTACTS.